Catch-and-release and size limit regulations for blue, white, and striped marlin: The role of postrelease survival in effective policy design

Catch-and-release fishing as a management and conservation tool for billfish (family Istiophoridae) is practiced in many recreational fisheries, and mandatory release of billfish has been implemented for some commercial fisheries. Inherent in these approaches is the observation that survival of released fish is greater than those that are landed. Recent studies using pop-up satellite tags have begun to quantify postrelease survival rates for billfish, yet the efficacy of management measures that require some or all billfish to be released have not been evaluated. Using an age- and size-structured population model that accounts for individual variability in growth, we simulated the effects of postrelease mortality on yield, risk of recruitment overfishing, efficiency (i.e., ratio of harvest to postrelease mortality), and probability of catching trophy-sized individuals for three marlin species. Regulations such as size limits, catch-and-release, and mandatory release are likely to provide some benefit to billfish populations, but our results show that the effectiveness of these strategies is reduced when release survival is less than 100%. The management approaches most likely to benefit billfish populations are ones that focus on maximizing postrelease survival in the recreational fishery and minimize the billfish catch in commercial fisheries.